High frequency tube



Dec. 3, 1957 B. c. GARDNER- 2,815,467 HIGH FREQUENCY TUBE Filed Dec. 23,1954 5 Sheets-Sheet l saw/11 INVENTOR.

Armeflev B. C. GARDNER HIGH FREQUENCY TUBE Dec. 3, 1957' 3 Sheets-Sheet2 Filed Dec. 23, 1954 :EIl j a INVENTOR. efierlzard'rgfarai zen .BY

fi/fl 74AM Aria/FIVE? Dec. 3, 1957 B. c. GARDNER 2,315,467

HIGH FREQUENCY TUBE Filed Dec. 25. 1954 5 Sheets-Sheet 3 IN V EN TOR.

ATTORNEY HIGH FREQUENCY TUBE Bernard C. Gardner, Los Altos, Califl,assignor to Varian Associates, San Carlos, Califl, a corporation ofCalifornia Application December 23, 1954, Serial No. 477,157

.13 Claims. (Cl. 315-5.21)

This invention relates generally to ultrahigh frequency tubes and hasreference, more particularly, to novel ultrahigh frequency reflexklystrons.

Ultrahigh frequency reflex klystrons or velocity modulation tubesemploying a cavity resonator and electron beam reflector as heretoforeconstructed have been relatively expensive to produce owing to the useof expensive multiple exacting machine operations necessitatingextremely accurate manufacture and assembly.

The principal object of the present invention is to provide a novelreflex klystron tube that is of relatively simple rugged constructionand easily fabricated largely of pressed metal parts whereby the overallcost of a tube of this general type is greatly reduced.

Another object of the present invention is to provide a novel reflexklystron that is extremely stable as to frequency and has a long life inuse, with low distortion and which is suitable for transmitter-receiverservice in microwave relay systems, as a local oscillator, a radiofrequency generator as well as for other uses.

Another feature of the present invention is to provide a novel tube ofthe above character that has an external cavity portion of exceptionalfrequency stability so that the tube has substantially negligiblefrequency drift in use, said tube being externally tuned to eliminatecomplicated tuning structures and being adapted to be mass-produced atminimum cost.

A further feature of the present invention is to provide a novel tubestructure comprising component parts which may be fabricated into aseries of tubes of differing fre quency ranges without the necessity ofchanging the dimensions of the parts used.

Other features and advantages of the present invention will becomeapparent from a perusal of the following specification taken inconnection with the following drawings wherein the invention isembodied.

In the drawings,

Fig. 1 is a part longitudinal sectional view of the novelreflexklystronof the present invention,

Fig. 2is a part sectional view taken along lines 2-2 of Fig. 1,

Fig. 3 is a part sectional view taken along lines 3-3 of Fig. 2, and

Fig. 4 is a view similar to Fig. 1 of a somewhat modified structure. i A

Similar characters of reference are used in the above figures todesignate corresponding parts;

Referring now to Figs. 1 to 3 of'the drawings, the reference numeral 1designates a housing or bulb portion of the novel tube of this inventionwithin which the cathode or gun assembly 2 is contained. This cathodeassembly has a-cylindrical vitreous sealing base 3 having a flange 18supportedupon and secured to a ring member 4 that is'braz'ed at 5 to astepped or flanged portion of the bulb 1. The joint 5 together with theflange 4 and sealing'base 3 serve to seal off the bottom of the bulb 1so that a vacuum may be maintainedw-ithin this in Rise. A tubebas'e 7'of plasticoi' other suitable insunited States atent lating materialhaving terminals 8 is secured to the outer free end of bulb 1 as bycrimping of the material of this bulb into recesses provided in theperiphery of tube base 7 as indicated at 9.

The cathode button 10 is shown as of the convex focusing type and isindirectly heated by a heating coil 11 supplied through leads 13connected to terminals 8. Coil 11 is contained within a cylindricalhousing 12 which also carries the button 10, housing 12 in turn beingsupported by brackets or straps 14 fixed upon the inner wall of a hollowcylindrical support, and heat shield 15 as by spotwelding thereto.Support 15 also serves as a focus electrode for the electron beamemitted from the cathode button 10. This combined focus electrode heatshield and supporting member is formed by die pressingsheet metal and isprovided with outwardly struck ears 16 in its lower portion forsupporting this member as by spotwelding to the stem wires 17 projectingfrom the base 3.

A hollow cylindrical anode 20, having a slightly conical or dishedwasher like anode header 21 assembled thereon as by brazing, is insertedwithin the bulb 1 concentrically with the cathode button 10 so that theelectron beam leaving this button in use passes through the hollowinterior of anode 20.

The washer-like anode header 21 surrounds the anode 20 and supports thesame upon the inner walls of the bulb 1. In assembling the header 21upon the anode 20, the former is adjusted longitudinally along thelength of the anode 20 as shown by the dot dash lines in Fig. 1 tothereby vary the size of the resonant cavity to suit the frequency rangedesired. This arrangement allows the use of a fixed length gun assembly2 for a complete series of tubes of differing specific frequency ranges.

The inner end of the hollow anode 20 is provided with a grid 22 which issomewhat spaced from an opposed grid 23 shown mounted in a ring 24secured to the inner end 25 of the bulb 1. The inner end 25 of a secondbulb 1'- is secured to the end 25 in abutting relation as by brazing. Areflector 26 is positioned opposite the grid 23 and spaced therefrom forreflecting the electrons back into the resonant cavity 27 formed withinbulb 1, header 21 and anode 20. The reflector 26 is of substantiallycup-shape and is pressed from sheet metal and is provided with anexternal apron or cylindrical portion 28 which apron extends outwardlyand is provided with bent out ears 29 to which supporting stem wires 17are secured as by spotwelding. The wires 17' are carried by a sealingbase 3 similar to base 3 which base is supported by a ring member 4secured as by brazing 5 to the flange or step portion 6' of bulb 1'. Theouter end of the portion 1 is closed by a base or cover 7' similar tothe base 7, the cover 7 of plastic or other insulating material beingsecured to the outer free end of bulb 1 by crimping the material of thebulb into recesses provided in the periphery of the cover 7 as indicatedin 9'. An external central conducting stem 30 is providedon the cover 7and is electrically connected to one of the wires 17' as by lead 31.

Thus it will be seen that the bulbs 1 and 1' together with their cathodeand reflector assemblies can be fabricated largely from similar standardpressed metal parts, the stem wires 17 and 1'7 serving to respectivelysupport the cathode assembly and the reflector assembly therebyeliminating special mounting struts for these members. The cathodeassembly including the focus electrode 15, the anode 20 and thereflector 26 are all automatically centered so as to be truly concentricduring the assembly of the tube. Where it is desired to maintain a fixedreflector voltage for a series of tube types having differing frequencyranges, it is necessary to change the length of the wires 17 somewhat soas to vary the spacing between grid- 23 and reflector 26. However, wherea fixed refiector voltage is not necessary the Wires 17' can all be madeof the same length for a complete series of tubes of progressivelyvarying operating frequencies. One side of the bulb 1 is pressed in asindicated at 32 making the transverse cross section of the bulb have aD-shape to provide a flat wall portion of appreciable extent so as toaccommodate a relatively long and somewhat narrow transverse irisopening 33. By thusly making this opening long and narrow the anodeheader 21 can be moved up and down within the inner portion of bulb 1without covering a portion of this iris opening.

Positioned externally of the flat wall 32 is an external resonatorportion 54 comprising sections 34 and 35 having abutting flanges 36 thatmay be soldered or otherwise secured together. Section 34 is formed withan inner flat end 37 abutting and secured to the flat wall 32. The wall37 is provided with a window 38 that is aligned with iris opening 33 butis appreciably larger than this opening as illustrated in Figs. 1 and 3.Positioned within the section 34 and in abutting relation to the endwall 37 is shown a plate member 39 having an opening 40 therein that issimilar to window 38 but again is larger than this window for receivinga mica closure 41 that is sealed as by glass 42 around its edges to theplate 39. Since opening 40 is a good sized opening it is possible toemploy a good sized piece of mica for effecting the closure of thewindow 38 thus enabling easy assembly of this portion of the tube. Also,since the iris opening 33 is smaller than the window 38, the tendencyfor sealing glass to overlap the iris opening 33 is substantiallyeliminated. Hence a sharp clear cut aperture is provided for the passageof energy from within resonator 27 into external resonator portion 54,the latter resonator portion being sealed off from the evacuated innerresonator portion 27. A screw 43, which preferably is inclined, isthreaded through the wall of section 34 and is directed toward thewindow 38 for concentrating the electromagnetic field in the vicinity ofthis window and enhancing the passage of energy through the window andinto the external cavity 54. Once this screw 43 has been adjusted toobtain optimum energy interchange it can be locked in place as by spotwelding and the screw slot filled by a sealing composition 44, ifdesired, to prevent unnecessary tampering with the screw adjustment.

To effect the tuning of the tube without physically distorting the wallsthereof which is undesirable since it increases microphonics andincreases the possibility of leaks and lowers the tube frequencystability, a tuning screw 45 is employed which is threaded through ablock 46 mounted on the section 35, the screw projecting into thissection. A leaf spring tension device, comprising a leaf spring lockwasher 47, which presses at one side against the block 46 and its otherside carries a nut 48 fixed therein and through which the screw 45 isthreaded, serves to hold the screw in adjusted position and againstturning. Thus, to vary the tuning of the tube it is merely necessary toturn the screw 45, the setting of the screw being retained in fixedposition by the spring tension device described.

When it is desired to use the tube of this invention to cover a seriesof separated frequency ranges use may be made if desired of waveguideridges 49 shown in full and in dot dash lines in Fig. 1 of the drawingsto aid in obtaining the desired frequency range, one of these ridgesalso being shown in Fig. 3, said ridges having the effect of changingthe effective electrical dimensions of the external cavity 54. Amounting flange 50 is shown secured as by brazing to the section 35, theflange 50 being adapted to be connected to a similar flange provided onan input of the equipment to which the tube is connected. In practice ithas been found that a considerable series of ranges of operatingfrequency can be obtained without employing the ridges 49 by merelyadjusting the screw 45 and at times varying the size of the outputopening in flange 50. The tube is shown provided with cooling fins 51spaced apart by spacers 52 and mounted upon the reduced portions ofbulbs 1 and 1'. These fins and spacers can be slid over the bulb andbrazed in place during the assembly of the tube.

In use, the tube has good inherent temperature compensation by virtue ofthe fact that not only cooling is provided by use of fins '51 togetherwith the use of heat conducting thin pressed metal parts but as the tubeheats up in use the tendency of cavity 27 to enlarge and increase ininductance is compensated for by the action of the slightly outwardlydished anode header 21 having a coefficient of thermal expansion largerthan the coeflicient of thermal expansion of the cavity side walls. Thisheader as of, for example, copper acts to move the anode 20 downwardlyslightly, as viewed in Fig. 1, while the tube body, as of steel, heatsup thereby slightly increasing the spacing of grids 22 and 23 andlessening the capacity therebetween and hence compensating for theincreased inductance of the resonator, thereby maintaining the operatingfrequency of the tube substantially constant.

Fig. 4 of the drawings illustrates a structure similar to the precedingfigures with the exception that the anode 20 is of such dimensions as toreceive the cathode 10 and its focusing electrode 15' therewithin,thereby enabling the cathode to be placed relatively close to theresonator gap and enabling good control of the optics of the tuberegardless of the adjustment of the anode header 21' along the exteriorsurface of the anode 20'. In this form of the invention an acceleratinggrid 53 is shown carried by the interior wall of anode 20' andpositioned opposite the cathode button 10' to aid in focusing the beamthrough the tube gap. Otherwise this construction is similar to that ofthe preceding figures.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A high frequency tube comprising two similar bulb members havingopposing ends secured together and carrying a first grid, a hollow anodeprovided within one of said bulb members and having a grid at one endthereof in axial alignment with and opposing said first grid and spacedtherefrom, an anode header extending between said anode and the walls ofsaid bulb member, said header being positioned intermediate said gridand the other end of said anode to form a cavity resonator therewithinof dimensions suitable for a selected frequency range, similar cathodeand reflector sealing base members carried respectively by said bulbmembers in axial alignment with said anode, said cathode base membercarrying a cathode assembly and said reflector base member carrying areflector, said cathode assembly serving to direct a beam of electronsthrough said anode, said resonator and said grids toward said reflectorfor reflection back into said resonator.

2. A high frequency tube as defined in claim 1 wherein said cavityresonator is provided with a wall portion having a relatively longnarrow transverse iris opening therein, whereby said anode header duringthe fabrication of the tube may be variably positioned longitudinallywithin said cavity resonator corresponding to differing operatingfrequencies of said tube without covering said iris opening. 7

3. A high frequency tube as defined in claim 2 wherein said cavityresonator is provided with an external resonator portion having a windowopening therein aligned with the iris opening of said resonator, saidwindow opening being appreciably larger than said iris opening, and asealing closure for said window, said closure serving to seal off thecavity resonator while at the same time permitting the passage of energytherefrom into said external resonator portion.

4. A high frequency tube as defined in claim 3 wherein said externalresonator portion is provided with a threaded aperture adjacent saidwindow, and a screw threaded through said aperture and terminating inthe vicinity of said window for concentrating the electromagnetic fieldin the vicinity thereof to enhance the passage of electromagnetic energytherethrough.

5. A high frequency tube as defined in claim 4 wherein said externalcavity resonator is provided with an adjustable tuning screw threadedthereinto, and tension means for holding said screw in adjustedposition.

6. A high frequency tube comprising opposed similar sheet metal bulbssecured together at their abutting inner ends, said abutting ends beingcentrally apertured, a grid in said aperture for permitting the passageof an electron beam, the outer ends of said bulbs being formed withoutwardly offset portions providing internal seats, a cathode assemblypositioned within one of said bulbs for emitting electrons for passagewithin said bulbs, a reflector assembly positioned within the other ofsaid bulbs for reflecting the electrons back toward said cathode,similar sealing bases for said bulbs having outwardly projecting flangemembers secured to said seats, said sealing bases respectivelysupporting said cathode and reflector assemblies in axial alignmentwithin said bulbs.

7. In a thermionic tube, a casing comprising two similar hollow bulbmembers having inner abutting ends affixed together, similar sealingbase members mounted for closing and sealing off the outer portions ofsaidbulb members, a cathode assembly positioned within the first of saidbulb members and carried by its base member, a reflector assemblypositioned within a second of said bulb members and carried by its basemember and a cavity resonator within said first bulb member, theabutting ends of said bulb members being apertured for receiving anelectron beam passing from said cathode assembly through said resonatortoward said reflector, and similar base members closing the outer endsof said bulb members.

8. A thermionic tube as defined in claim 7 wherein said cavity resonatoris provided with a cylindrical anode surrounding the electron beam andan anode header plate secured to said anode for determining theoperating frequency of said tube, said header plate being slightlydished to effect automatic temperature compensation of said tube.

9. A thermionic tube as defined in claim 7 wherein said sealing basemembers have conducting wire stems extending therethrough, saidreflector assembly and said cathode assembly having projecting ears towhich said wire stems are attached, to thereby support said assemblieswithin said tube casing, and from said base members, said base membershaving outwardly extending ring members secured to said bulb members forpositioning said reflector and cathode assemblies axially within saidtube.

10. A thermionic tube as defined in claim 7 wherein said cavityresonator is provided with an external resonator portion having a Windowopening therein communicating with said cavity, a sealing closure insaid window, said closure serving to seal off the cavity resonator whileat the same time permitting the passage of energy therefrom into saidexternal resonator portion, and a metallic member carried by saidexternal resonator portion and extending close to said Window forconcentrating the electromagnetic field in the vicinity thereof toenhance the passage of electromagnetic energy therethrough forutilization.

11. A high frequency tube comprising a temperature compensated resonantcavity having a re-entrant portion and adapted for electromagneticinteraction with a beam of electrons passable therethrough, said cavityhaving side Walls and end walls, one end wall being provided with anoutwardly dished portion, said outwardly dished cavity end wall having acoeflficient of thermal expansion higher than the coefficient of thermalexpan sion of the cavity side walls whereby as the operating temperatureof the cavity is increased the gap spacing between the re-entrantportion and an end wall is increased in variable accordance with thetemperature to maintain a substantially constant resonant frequency in afluctuating thermal environment.

12. A high frequency tube body adapted to contain therewithin a cavityresonator for electromagnetic interaction with a beam of electronspassable therethrough comprising two sheet metal bulb members havingoppos ing ends coupled together, one of said bulb members having asubstantially flat side wall portion providing a transversecross-section of the tube body with a portion of substantially D-shapeto facilitate coupling of said bulb to an external wave propagatingstructure, said fiat side wall portion of said bulb member having arelatively long and narrow transverse coupling slot therein forproviding a wave energy communication path between the relativelyshallow cavity resonator contained within the tube body and the externalWave propagating structure.

13. In a high frequency tube apparatus, a cathode assembly for providinga beam of electrons, a cavity resonator adapted for electromagneticinteraction with a beam of electrons passable therethrough, a reflectorfor returning the beam of electrons through said cavity resonator forsuccessive electromagnetic interaction, said reflector comprising aunitary thin walled tubular member closed off at one end by an inwardlydished transverse wall provided with a hollow rounded peripheral flange,said member having radially projecting ears at the other end thereof forcoupling to a plurality of supporting members.

References Cited in the file of this patent UNITED STATES PATENTS2,490,030 Cooke et a1 Dec. 6, 1949 2,508,346 Lafierty May 16, 1950

